Flippers from Around the World: We are not happy!

Posted by By Scuba Herald at 7 September, at 19 : 32 PM Print

Bottlenose dolphins suffering from food shortages may be killing their sibling species to take out the competition, scientists have warned.

A series of dead porpoises and young bottlenose dolphins washed up the country’s coastline have borne the animal’s teeth marks.

But the appearance of the body of a rare baby Risso’s dolphin on a beach in the Scilly Isles has raised fears that bottlenose dolphins may be becoming more aggressive in its desperate search for food.

The latest victim, which washed up in St Agnes, was young enough to still be dependent on its mother for nourishment and researchers believe it was killed by an adult predator.

Risso’s dolphins have tall dorsal fins, extensively-scarred, almost stripy black bodies and blunt heads. They are often seen around Cornwall although not as frequently as bottlenose and common dolphins. It is the first time one has been linked with a fatal attack by bottlenoses.

The baby dolphin has been brought back to the mainland where it will undergo a post-mortem examination.

Jan Loveridge, volunteer co-ordinator for Cornwall Wildlife Trust’s Marine Strandings Network, said: “Despite their friendly image bottlenose dolphins can be aggressive towards one another and on the rare occasion that we see a dead bottlenose wash ashore it often has rake or tooth marks inflicted by its own species.

“But we have recently begun to see an increase in the numbers of young and female harbour porpoise that have clearly been attacked by bottlenose dolphins and results from the post mortems carried out on these animals confirm this.

“The discovery of yet another species that has suffered from these attacks is of particular interest especially as it was so young.

“The motives for such attacks are unclear, although scientists have considered that competition for declining food stocks may trigger the behaviour.”

Dr Peter Evans, director of Sea Watch Foundation, said the Risso’s dolphin may simply have been mistaken for a porpoise.

“Risso’s dolphins feed on things like squid and cuttlefish and octopus, which are rarely eaten by bottlenose dolphin, which feed predominantly on fish,” he said.

“It was quite possible that it was quite vulnerable because of its size and was mistaken for a porpoise. Young Risso’s look a bit like porpoises.”

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